results, doctors could pick up early stages of the disease with almost 100% accuracy. >> it is only when you look at it over time that it starts to become much more effective at picking up early stage disease. >> reporter: based on those results, some women had ultrasounds to look for a cancerous mass, and if necessary, surgery. about halfway through the study, liz degalle's ca-125 numbers were up, and she was diagnosed with early stage ovarian cancer. >> i just thought i was tired. i had some pain, different places, but nothing on a regular basis. >> reporter: that is common. the reason so many women aren't diagnosed until the cancer has spread. the problem, symptoms are often vague and can mimic other ailments. they may include abdominal discomfort, including bloating, cramps, changes in bowel habits, back pain and abnormal bleeding. doctors say there may be cause for concern if any of these last for more than a few weeks.